This invention relates to apparatus for inspecting objects in difficult to access locations, and more particularly to apparatus for inspecting and making measurements of the surfaces of components of nuclear power plant steam generators.
There is a need for tools specifically designed for inspecting the internal components of nuclear power plant steam-generators and associated components. The steam-generator functions as a heat exchanger; transferring energy between (primary) water circulating through the reactor core to (secondary) water circulating through the generator turbine. Though the water on the secondary side is maintained at a high level of purity, high temperatures, trace chemicals, and rapid fluid flow rates lead to scouring and corrosion of the steam-generators internal parts and associated plumbing. Chemical action and re-deposition leads to a problem of on-going accumulating deposits on critical surfaces on the secondary side such as flow tubes and support plate surfaces. This type of deposit accumulation can lead to a serious reduction in heat transfer efficiency, flow-tube cracking, and mechanical loading of internal parts.
To effectively monitor the progression and effects of corrosion and accumulating deposits it is necessary to perform visual inspections on the secondary side of the steam-generators interior parts and associated plumbing. The devices shown in U.S. Pat. Nos. 5,544,206, 5,265,129 and co-pending application Ser. No. 08/874,139 can perform this type of inspection effectively. As a result of the systems capabilities of these devices, regular internal visual inspections of nuclear power-plant steam-generators have become an important and necessary part for many plant maintenance programs. Despite the success of the current devices, there is a need to improve and expand inspection capabilities. Currently, the data provided by known inspection systems is in the form of simple 2-Dimensional (2-D) video imagery. Visual data is typically collected by a miniature CCD (Charge-Coupled-Device) camera mounted on the end of a telescoping boom or extendible wand/telescoping boom combination. The extendible boom moves the camera and associated hardware through narrow slots within the steam-generators support plates to a point of interest. The acquired video inspection data from the mounted camera is then stored on video tape for post analysis and evaluation. Lacking depth information, there is no way to accurately measure distances from the observed video images. Hence, valuable corrosion and deposit thickness information cannot be analytically determined. This type of information would be valuable to nuclear plant managers because it would give them the ability to track the rate of steam generation degradation given subsequent and similar inspections. It is an object of this invention to provide a 3-Dimensional (3-D) profiling system to accurately determine spatial information from an inspected image field.
It is another object of this invention to provide apparatus of the type heretofore known having an articulated inspection wand having a three-dimensional profiling system integrated therewith that is small enough to be moved into position to inspect components of a nuclear power plant steam generator. Briefly stated, and in accordance with a presently preferred embodiment of the invention, apparatus for inspecting the surfaces of inaccessible objects such as the components of a nuclear power plant steam generator includes: an articulated inspection wand having a proximal end and a distal end movable into position adjacent the surface to be inspected, a laser light source located remotely from the distal end, first and second position sensing detectors located remotely from the distal end of the wand, first and second extending imaging light guides extending from the laser light source, and the position sensing detectors to the distal end of the wand.
In accordance with another aspect of the invention, first and second optical lenses are disposed at the distal ends of the second and third imaging light guides for forming an image of the surface to be inspected.
In accordance with another aspect of the invention, focusing lenses are positioned between the proximal ends of the extended imaging light guides and the first and second position sensing detectors.
In accordance with another aspect of the invention, a two-dimensional scanner is disposed between the laser light source and the proximal end of the first extended imaging light guide.
In accordance with another aspect of the invention, an image capturing device, such as a video camera is optically coupled to the second extended imaging light guide.
In accordance with a still further aspect of the invention, an illumination light source is coupled to at least one of the second and third extending imaging light guides, for providing illumination of the surface for the video camera.
In accordance with another aspect of the invention, beam splitters are provided at the proximal ends of the imaging light guides for coupling the light guides to the illumination sources and the position sensitive detectors.